As to a conventional heat exchanger of this type, there is a heat exchanger disclosed in Patent Document 1. As illustrated in FIG. 11 to FIG. 13, this heat exchanger 100 has first plates 101 and second plates 102 alternately laminated therein, and in each of the plates 101 and 102, a pair of first communication holes 103 and a pair of second communication holes 104 are formed, respectively. Each of the plates 101 and 102 has an outer peripheral wall 105 protruding toward the same direction of a laminating direction, and the outer peripheral walls 105 adjacent to each other come into contact with each other. Furthermore, a first coolant flow path 106 and a second coolant flow path 107 are alternately provided between the adjacent plates 101 and 102. Each of the first communication holes 103 is opened and each of the second communication holes 104 is closed, to the first coolant flow path 106, and each of the second communication holes 104 is opened, and each of the first communication holes 103 is closed, to the second coolant flow path 107.
In the configuration described above, a first coolant that flows via a coolant inlet portion 108 flows into the first coolant flow path 106 from one side of the first communication holes 103, passes through the first coolant flow path 106, and then, flows out of the other side of the first communication holes 103 via a coolant outlet portion 109. A second coolant that flows via a cooling-water inlet portion 110 flows into the second coolant flow path 107 from one side of the second communication holes 104, flows through the second coolant flow path 107, and then, flows out of the other side of the second communication holes 104 via a cooling-water outlet portion 111. The first coolant and the second coolant exchange heat via the first plate 101 or the second plate 102 during the process of flowing through each of the first coolant flow path 106 and the second coolant flow path 107.
In the heat exchanger 100 having a laminated form as described above, the first plate 101 and the second plate 102 are fixed through brazing in a state where portions of the first plate 101 and the second plate 102 required to be joined are brought into close contact with each other by applying a load, with a jig or the like during brazing, in the laminating direction of the first plate 101 and the second plate 102. At this time, the load applied in the laminating direction is preferably large because the degree of close contact at the potions required to be joined is increased, as long as the first plate 101 and the second plate 102 are within the range of not being deformed.
Furthermore, portions of the first plate 101 and the second plate 102 where the first communication hole 103 or second communication hole 104 is opened have a weaker strength than that of other portions, and it is necessary to achieve a highly airtight structure by reliably brazing the peripheries of the first communication hole 103 and second communication hole 104, where coolant with higher pressure flows. Specifically, in the case where coolant with higher pressure flows into the first coolant flow path 106, it is necessary to perform brazing so that the first communication hole 103 and the first coolant flow path 106 are shielded in a highly airtight manner.